If you buy the Hydor ETH brand heater,model 200 is the only model that will connect to 1/2" return line . Models 201 and 300 have 5/8" inlet/outlet connections.I don't own one but heard they are the best. Not sure about the hose sizes on the cascade line.If you don't go with an external heater,Won Brothers titanium is the best submersible.When you say glass tubing,do you mean internal heater?

Someone mentioned glass tubing on the inside of the tank as the intake, and return for the filter, so it can't be seen at all.

Thanks for the info on the heater, it is pricy, but I think worth it, and it will allow more room, and less un-natural stuff to look at in the tank :: ) Just gotta find out what size tubing the cascade uses lol.